AU3183299A - High efficiency low pollution hybrid brayton cycle combustor - Google Patents

Abstract

An energy conversion system having a combustor (200) including a combustion chamber (25) therein, means for delivering fuel, air, and liquid thermal diluent to the combustor, whereby combustion results in creation of an energetic fluid comprising thermal diluent, combustion products and residual components in the air and fuel for delivery to a utilization device, and a controller for the delivery means. The controller is operative to control the amount of air and fuel being delivered so that substantially all of the fuel, and a majority of the oxygen in the air is consumed in the combustion process; and to control the quantity and location of delivery of thermal diluent to the combustor to achieve, substantially through heat absorption by the thermal diluent, a desired combustion flame temperature, a desired combustor temperature profile, and an acceptably low pollutant content in the energetic fluid exiting the combustor.

Description

WO 99/46484 PCT/US99/05271 1 HIGH EFFICIENCY LOW POLLUTION HYBRID BRAYTON CYCLE COMBUSTOR BACKGROUND This application is a continuation-in-part of U.S. Application Serial No. 08/232,047 filed April 26, 1994 now U.S. Patent 5,743,080 issued April 28, 1998 which is the U.S. National Stage of PCT/US93/10280 filed 5 October 27, 1993 and a continuation-in-patent of U.S. Patent 5,617,719 filed October 27, 1992 all of which are incorporated by reference. The invention herein constitutes the new matter not disclosed in said prior applications and patents. FIELD OF THE INVENTION 10 The present invention is directed to a vapor-air steam engine which operates at high pressure and utilizes a working fluid consisting of a mixture of fuel combustion products and steam with a minimal amount of excess compressed air. The invention is further directed to processes for producing electrical energy, usable shaft horsepower and/or large quantities of steam 15 in a fuel burning system at high efficiency and low specific fuel consump tion, while generating insignificant amounts of environmental pollutants (NOx, CO, particulates, unburned fuel). The invention is still further directed to the production of potable water while generating electrical power without polluting the environment or significantly reducing the efficiency or increas 20 ing the fuel consumption. BACKGROUND OF THE INVENTION Internal combustion engines are generally classified as either constant volume or constant pressure. Otto cycle engines operate by exploding volatile fuel in a constant volume of compressed air while diesel cycle WO 99/46484 PCT/US99/05271 2 engines burn fuel in a modified cycle, the burning being approximately characterized as constant pressure. External combustion engines are exemplified by steam engines, steam turbines and gas turbines. It is well known to supply a gas turbine with a 5 gaseous working fluid generated by combusting a fuel with compressed air and to operate various motor devices from energy stored in this high pressure gaseous stream. In these devices, temperature control is usually the result of feeding large quantities of excess compressed air. It is also known to burn fuel in a chamber and exhaust the combus 10 tion products into a working cylinder or chamber, sometimes with the injection of small quantities of water or steam. These may also be classi fied as external combustion engines. Some other devices have been proposed in which combustion chambers are cooled by addition of water or steam provided either internally 15 or externally. Still another form of apparatus has been proposed for opera tion on fuel injected into a combustion cylinder as the temperature falls, having means to terminate fuel injection when the pressure reaches a desired value. Each of these prior engines has encountered difficulties which limit 20 their general adoption as a power source for the operation of prime movers. Among these difficulties have been the inability of such an engine to meet sudden demand and/or to maintain a constant working temperature or pressure as may be required for efficient operation of such an engine. Furthermore, control of such engines has been inefficient, and the 25 ability of the gas generator to maintain itself in standby condition has been wholly inadequate. In all practical applied engine configurations the require ment for cooling the confining walls of the work cylinders has resulted in loss of efficiency and a number of other disadvantages previously inherent in internal combustion engines. 30 The present invention overcomes the limitations of the prior art described above. First, the requirement of large amounts of excess com- WO 99/46484 PCT/US99/05271 3 pressed air or external liquid cooling is eliminated by injecting water directly into the combustion chamber to control the temperature of the resulting working fluid. When water is injected it is converted instantaneously into steam in the combustion chamber, and it becomes a component of the 5 working fluid itself, thus increasing the mass and volume of the working fluid without mechanical compression. In the present invention, independent control of the a) combustion flame temperature b) combustion chamber temperature profile by liquid water injection and c) fuel to air ratio allows the physical properties of the 10 working fluid to be optimized for high efficiency operation. Reducing or eliminating excess air, thus limiting the availability of excess oxygen, and controlling the flame temperature and combustor temperature profile also prevents the formation of NO x , and favors the complete conversion of burning fuel to C02, minimizing CO production. 15 The present invention also utilizes high pressure ratios as a way of increasing efficiency and horsepower while simultaneously lowering specific fuel consumption ("SFC"). When water is injected and converted into steam in the combustion chamber of the present invention, it acquires the pressure of the combustion chamber. It should be noted that the pressure 20 of the combustion chamber is acquired by the steam irrespective of the pressure ratio of the engine. Thus, a higher pressure ratio can be obtained in the engine without expending additional work for performing compression for new steam or water injection. Because of the injection of massive amounts of water in the present invention, there is no need to compress 25 more air than needed for combustion, this excess air typically used in prior art systems for cooling. The elimination of this requirement results in an enormous energy savings to the system and a significant increase, without additional consumption of fuel, in the available shaft horsepower without increasing turbine speed. 30 Water injection, as taught in the present invention, provides several advantages over the prior art. First, a minimal amount of additional work is WO 99/46484 PCT/US99/05271 4 required to pressurize water above the combustion chamber pressure. In steam injection system significant work must be expended to raise the steam to a pressure above that of the combustion chamber. Likewise, excess air requires additional work be expended to raise the feed air to 5 higher pressures to produce additional working fluid mass. Furthermore, when water is injected and converted to steam in the present invention, it acquires the pressure of the combustion chamber without additional work. This steam also has constant entropy and enthalpy. In the present invention excess (waste) heat from combustion is used 10 to convert injected water to steam, thus increasing the working fluid pressure and mass of the working fluid without mechanical compression of excess air. In contrast, in a typical Brayton Cycle Turbine, 66% - 75% of the mechanically compressed air is used to dilute the products of combus tion in order to reduce the temperature of the working fluid to the desired 15 Turbine Inlet Temperature ("TIT"). The steam generated by vaporization of the injected water can at least double the mass of the combustion generated working fluid and increase the net horsepower by 15% or more. Therefore, the water can be seen to serve as a fuel in this new thermodynamic system because it 20 supplies pressure, mass, and energy to the system, resulting in an increased efficiency of the present system. The cycle of the present invention may be open or closed with respect to water. That means that the air and water may be exhausted (open) or recovered and recycled (closed). Desalination or water purification 25 can be a byproduct of electric power generation from a stationary installa tion or water borne ships, where the cycle is open as to air but closed as to the desalinated water recovery. Marine power plants, industrial applica tions, drinking water and irrigation water clean up and recovery systems are also viable applications.

WO 99/46484 PCT/US99/05271 5 The present cycle can also be employed in the closed cycle phase in mobile environments, e.g. autos, trucks, buses, rail locomotives, marine craft, commuter aircraft, general aviation and the like. SUMMARY OF THE INVENTION 5 One of the objectives of this invention is to provide a new, thermody namic power cycle, which can operate in an open or closed mode, that compresses a stoichiometric amount of air and combusts fuel with the air so as to provide efficient, clean, pollution free power. It is also an object of this invention to completely control the temper 10 ature of combustion within a combustor through the employment of the latent heat of vaporization of water without the necessity to mechanically compress excess (dilution) air for cooling. A further object of this invention is to reduce the air compressor load in relation to a power turbine used in the engine so that a smaller compres 15 sor can be used and slow idling and faster acceleration can be achieved. A further object of this invention is to separately control the turbine inlet temperature (TIT) on demand. Another object of this invention is to vary the composition and temperature of the working fluid on demand. 20 It is also an object of this invention to provide sufficient dwell time of the reactants in the combustion chamber to permit stoichiometric combus tion, chemical bonding, and time for complete reaction and quenching, resulting in chemical equilibrium. It is also an object of this invention to combust and cool the products 25 of combustion in a manner which will prevent the formation of smog causing components such as NO x , unburned fuel, CO, particulates, CO 2 dissociation products, etc. It is also an object of this invention to provide a combustion system with 100% conversion of one pound of chemical energy to one pound of 30 thermal energy.

WO 99/46484 PCT/US99/05271 6 It is also an object of this invention to operate the entire power system as cool as possible and still operate with good thermal efficiency. It is also an object of this invention to provide a condensing process in order to cool, condense, separate, and reclaim the steam as condensed, 5 potable water. It is also an object of this invention to provide an electric power generating system which uses nonpotable water as its coolant and pro duces potable water as a byproduct of the electric power generation. It is also an object of this invention to provide a new cycle which 10 alternatively provides a modified Brayton cycle during one mode of engine operation, a vapor air steam cycle during a second mode of engine opera tion and a combined cycle during a third mode. It is also an object of this invention to provide a combustor for use with any turbine power generating system such that the power system 15 produces electrical energy at a greater efficiency and reduced specific fuel consumption when compared with currently available systems using cur rently available combustors. It is also an objective of this invention to provide a combustor which can be retrofit into current hydrocarbon fuel burning systems replacing 20 currently used combustors and eliminating the need for pollution abatement equipment (catalytic converts, reburns, scrubbing systems) while increasing operating efficiency and decreasing pollution in exhaust streams. It is also an object of the invention to provide a turbine power generation system which provides significantly increased usable shaft 25 power (net usable power) when compared with a Brayton cycle system burning an equivalent amount of fuel. It is also an object of this invention to provide a power generating system which produces electrical energy at an overall efficiency signifi cantly greater than 40%.

WO 99/46484 PCT/US99/05271 7 It is also an objective to provide a power generating system which burns hydrocarbon fuels in a more efficient manner to produce less green house gases (C0 2 ). It is also an objective to efficiently provide large quantities of steam 5 at any temperature and pressure desired. In accordance with one exemplary embodiment of the present invention, referred to as the VAST cycle, an internal combustion engine is described. This engine includes a compressor configured for compressing ambient air into compressed air having a pressure greater than or equal to 10 six atmospheres, and having an elevated temperature. A combustion chamber connected to the compressor is configured for staged delivery of compressed air from the compressor to the combustion chamber. Separate fuel and liquid injection controls are used for injecting fuel and liquid water respectively into the combustion chamber as needed and where needed. 15 The amount of compressed air, fuel and water injected and the temperature of the injected water and the point of injection into the combustor are each independently controlled. As a result, the average combustion temperature and the fuel to air ratio (F/A) can also be independently controlled. The injected fuel and a controlled portion of the compressed air are combusted, 20 and the heat generated transforms the injected water into a vapor. When the injected water is transformed into a vapor the latent heat of vaporization of the water reduces the temperature of the combustion gases exiting the combustor. An amount of water significantly greater than the weight of the combusted fuel is used. However, the mass of air feed to the system is 25 significantly reduced. As a result, the mass flow of combustion generated working fluid may be varied from 50% to greater than 200% of mass flows in current systems using the same amount of fuel under most operating conditions. A working fluid consisting of a mixture of a small amount of the 30 unburnable 79% non-oxygen components of the compressed air, fuel combustion products and water vapor is thus generated in the combustion WO 99/46484 PCT/US99/05271 8 chamber during combustion at a predetermined combustion temperature and combustor temperature profile. Substantially all of the temperature control is provided by the latent heat of vaporization of the water. Any excess is provided only to assure complete combustion and is not provided for 5 cooling purposes. This working fluid can then be supplied to one or more work engines for performing useful work. Alternatively, the working fluid, which is high temperature, high pressure steam can be used directly, such as injection in oil wells to increase flow, as a heat source for distillation towers or other equipment which utilize steam for operation. 10 In more specific embodiments of the present invention, an ignition sparker is used to start the engine. The engine may also be operated either open or closed cycle; in the latter case, a portion of the working fluid exhaust may be recuperated. The flame temperature and combustion chamber temperature profile are monitored using temperature detectors and 15 thermostats located throughout the combustor. Further, a computerized feedback control system may be used to monitor the gaseous components of the exhaust stream and operating conditions and feed rates can be automatically adjusted to minimize NO x and CO in the exhaust. 20 When the present invention is used, the combustion temperature is reduced by the combustion control means so that stoichiometric combus tion and chemical reaction equilibrium are achieved in the working fluid. All chemical energy in the injected fuel is converted during combustion into thermal energy and the vaporization of water into steam creates cyclonic 25 turbulence that assists molecular mixing of the fuel and air such that more complete combustion is effectuated. The injected water absorbs all the excess heat energy, reducing the temperature of the working fluid to the maximum desired operating temperature of the work engine. When the injected water is transformed into steam, it assumes the pressure of the 30 combustion chamber, without additional work for compression and without additional entropy or enthalpy. The careful control of combustion tempera- WO 99/46484 PCT/US99/05271 9 ture prevents the formations of gases and compounds that cause or contrib ute to the formation of atmospheric smog and, by virtue of the increased operating efficiency, reduces the amount of green house gases generated per usable energy produced. 5 In another embodiment of the present invention, electric power is generated using nonpotable water as its coolant, potable water being produced as a byproduct of the power or steam generation. In a third embodiment of the present invention (a new cycle) the engine can operate in three different modes. When the engine is operated 10 in excess of a first predetermined rpm (i.e. at a high RPM), water injection and the amount of compressed air combusted is kept constant as engine rpm increases. At an interim RPM, i.e. between a first (high) and second (low) predetermined rpm, the water to fuel ratio is increased as the amount of excess air is decreased. When the engine is operated at various speeds 15 below a second predetermined rpm (i.e. a low RPM), the ratio of injected water to fuel is held constant and the amount of compressed air combusted is held constant, excess air being substantially eliminated. The use of this new cycle results in increased horsepower at a lower rpm, slow idle, fast acceleration and combustion of up to 95% of the 20 compressed air at low rpm. A more complete understanding of the invention and further objects and advantages thereof will become apparent from a consideration of the accompanying drawings and the following detailed description. The scope of the present invention is set forth with particularity in the appended 25 claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG.1 is a block diagram of a vapor-air steam turbine engine in accordance with a present invention; FIG.2 is a schematic diagram of a preferred combustor; 30 FIG.3 is a cross-sectional view along line 3-3 of Fig. 2.

WO 99/46484 PCT/US99/05271 10 FIG.4 is a block diagram of a vapor-air steam turbine engine that includes means for recovering potable water in accordance with the present invention; FIG. 5 is a schematic drawing of one embodiment of the vapor-air 5 steam turbine engine shown by a block diagram in Figure 4. FIG. 6 is a schematic drawing of a second embodiment of a vapor-air steam turbine engine with potable water recovery capabilities incorporating features of the invention. FIG. 7 is a graph showing the effect of pressure ratio on thermal 10 efficiency for the vapor-air steam turbine engine of Figure 1. FIG. 8 is a graph showing the effect of pressure ratio on specific fuel consumption for the vapor-air steam turbine engine of Figure 1. FIG. 9 is a graph showing the effect of pressure ratio on turbine power for the vapor-air steam turbine engine of Figure 1. 15 FIG. 10 is a graph showing the effect of pressure ratio on net power for the vapor-air steam turbine engine of Figure 1. DETAILED DESCRIPTION OF THE INVENTION A. Basic Configuration Of The Present System Referring now to FIG. 1, there is shown schematically a gas turbine 20 engine embodying the teachings of the present invention. Ambient air 5 is compressed by compressor 10 to a desired pressure resulting in com pressed air 11. In a preferred embodiment, compressor 10 is a typical well known two or three stage compressor, and the ambient air 5 is compressed to a pressure greater than about four (4) atmospheres, and preferably 10 to 25 30 atmospheres. The temperature of the compressed air depends on the compression ratio. At a compression ratio of 30:1 the compressed air temperature is approximately 14240 R (9640 F). The flow of the compressed air 11 is controlled by an air flow controller 27 to a combustor 25. Combustors are well-known in the art. 30 However, in the present invention, the compressed air 11 is supplied in a WO 99/46484 PCT/US99/05271 11 staged, circumferential manner by air flow control 27 to the combustor 200 shown in Fig. 2 and more fully described below. The staged feed of the air allows controlling and limiting of combustion temperature (flame tempera tures) throughout the combustion chamber 25. The normally high peak 5 temperatures are reduced while still generating the same total energy output from the combustion. Fuel 31 is injected under pressure by fuel injection control 30. Fuel injection control is also well-known to skilled artisans. The fuel injection control 30 used in the present invention can consist of a series of conven 10 tional single or multiple fuel feed nozzles. A pressurized fuel supply (not shown) is used to supply fuel, which can be any conventional hydrocarbon fuel, such as diesel fuel #2, heating oil, preferably sulfur free, well head oil, propane, natural gas, gasoline and alcohols such as ethanol. Ethanol may be preferable in some applications because it includes or can be mixed with 15 at least some water which may be used for cooling combustion products, thus reducing the requirement for injected water. Also ethanol water mixtures have a much lower freezing point thus increasing the ability to use the engine in climates which have temperatures below 32'F. Water 41 is injected under pressure and at a preset but adjustable 20 rate by a pump controlled by water injection control 40 and may be atom ized through one or more nozzles, into the feed air stream, downstream of combustion into combustion chamber 25 or into the flame if desired as explained further below. The temperature within combustor 25 is controlled by combustion 25 controller 100 operating in conjunction with other elements of the present invention detailed above. Combustion controller 100 may be a convention ally programmed microprocessor with supporting digital logic, a microcom puter or any other well-known device for monitoring and effectuating control in response to feedback signals from monitors located in the com 30 bustion chamber 25, the exhaust stream 51(expanded working fluid 21) or associated with the other components of the present system.

WO 99/46484 PCT/US99/05271 12 For example, pressure within combustor 25 can be maintained by air compressor 10 in response to variations in engine rpm. Temperature detectors and thermostats 260 (only one is shown for clarity) within combustor 25 provide temperature information to combustion control 100 5 which then directs water injection control 40 to inject more or less liquid water as needed. Similarly, working fluid mass is controlled by combustion control 100 by varying the mixture of fuel, water and air combusted in combustor 25. There are certain well-known practical limitations which regulate the 10 acceptable maximum combustion temperature. Foremost among these considerations is the maximum turbine inlet temperature (TIT) which can be accommodated by any system. To effectuate the desired maximum TIT, water injection control 40 injects water as needed to the working fluid 21 to keep the combustion temperature within acceptable limits. The injected 15 water absorbs a substantial amount of the combustion flame heat through the latent heat of evaporation of such water as it is converted to steam at the pressure of combustor 25. For ignition of the fuel injected into combustor 25, a pressure ratio of greater than 12:1 is needed to effectuate self-compression ignition. How 20 ever, a standard ignition sparker 262 can be used with lower pressure ratios. As mentioned above, combustion controller 100 independently controls the amount of combusted compressed air from air flow control 27, fuel injection control 30, and water injection control 40 so as to combust 25 the injected fuel and substantially all of the oxygen in the compressed air. At least 95% of oxygen in the compressed air is combusted. If less than 100% of the 02 is combusted then sufficient 02 is available to complete stoichiometric bonding and for acceleration. When 100% of the air is consumed in the combustion process, forming C0 2 , no oxygen is available 30 to form NOx. The heat of combustion also transforms the injected water into steam, thus resulting in a working fluid 21 consisting of a mixture of WO 99/46484 PCT/US99/05271 13 compressed, non-combustible components of air, fuel combustion products and steam being generated in the combustion chamber. Pressure ratios from about 4:1 to about 100:1 may be supplied by compressor 10. TIT temperatures may vary from 750oF to 2300oF with the higher limit being 5 dictated by material considerations. However, a higher TIT can be provided if the turbine is fabricated from materials, such as ceramics or other refrac tory materials, which can resist higher temperatures. A work engine 50, typically a turbine, is coupled to and receives the working fluid 21 from combustion chamber 25 for performing useful work 10 (such as by rotating a shaft 54 for example) which, in turn, drives a load such as a generator 56, which produces electric energy 58, or the air compressor 10. While the present invention discusses the use of a turbine as a work engine, skilled artisans will appreciate that reciprocating, Wankel, cam or other type of work engines may be driven by the working fluid 15 created by the present invention. Because of pressure differences between the combustor 25 interior and the turbine exhaust, the working fluid expands as it passes by work engine 50. The expanded working fluid 51 is exhausted by exhaust control 60 at varying pressure, generally from 0.1 atmospheres to about 1 atm. 20 depending on whether a closed cycle with vacuum pump or open cycle is used. However, higher exhaust pressures are possible. Exhaust control 60 may also include a heat exchanger 63 and/or condenser 62 for condensing the steam 61 from the expanded working fluid 51 as well as a recompressor 64 for exhausting the expanded working fluid 51. The steam 25 condensed in condenser 62 exits as potable water 65. Figure 2 shows a schematic diagram of a preferred combustor 200, which incorporates features of the invention, having an inlet end 198 and an exhaust end 196. In the embodiment shown the combustor comprises three concentric stainless steal tubes 202, 206, 210 and inlets for air, 30 water and fuel. The inner tube 202 is the longest of the tubes, the middle tube 206 is the shortest tube and the outer tube 210 is of an intermediate WO 99/46484 PCT/US99/05271 14 length. The inner or central tube 202, in a particular embodiment, has an inner diameter of 5 inches and a wall thickness of about 1/2 ". There is approximately a one inch air flow space between each of the inner tube 202, the middle tube 206 and the outer tube 210 (the inner air flow space 5 204 and the outer air flow space 208, respectively). The inlet end of the middle tube 206 and the outer tube 210 each have a hemispheric head 224, 226 connected to the circumference of each respectively to form a closed space 228, 230 contiguous with the space between the tubes 204, 208, creating a flow path, as described below, from the exterior of the 10 combustor 200, through the space between the outer tube 210 and middle tube 206 (the outer air flows space 208) and then between the middle tube 206 and the inner tube 202 (the inner air flow space 204) and through burner 214. Covering the inlet end or head 212 of the inner tube 202, as shown 15 in Fig. 3, is an air feed plate 232 to which are attached nested tubes which comprise the burner 214. Burner 214 is formed by three concentric tubes with the inner fire tube 216 being 2 inches in diameter, the central fire tube 218 being about 3 inches in diameter and the outer fire tube 220 being about 4 inches in diameter. The fire tubes 216, 218, 220 are progressively 20 longer in length so that a straight line connecting the internal ends thereof form a flame containment cone 222 with an angle of the cone 222 being from about 50 to 90 degrees. The inlet end of the central fire tube 216 extends into the air feed chamber 228 formed between the hemispheric head 224 on the middle tube 25 206 and the inlet end of the central tube 202. As shown in Fig. 3, a second air feed plate 236 with holes 234 therein covers the inlet end of the inner fire tube 216. In addition, holes 234 are distributed around and through the periphery of the outer surface of the inner fire tube 216 where it extends into the air feed chamber 228. Centrally located and passing 30 through the hemispheric heads 224, 226 and the second air feed plate 236 is a fuel injection nozzle 218 positioned to deliver fuel from the exterior of WO 99/46484 PCT/US99/05271 15 the combustor 200 into the inlet end of other inner fire tube 216 where the fuel is mixed with the air passing into the inner fire tube 216. Air for combustion is fed at the desired pressure through one or more air inlets 240 in the outer hemispheric head 226. The air then flows along 5 the outer air flow space 208 between the middle tube 206 and outer tube 210 from the inlet end 198 to the exhaust end 196 where it impinges on the exhaust end plate 242 which joins, in a leak proof manner, the exhaust end 196 of the outer tube 210 to the outer surface of the inner tube 202. It then flows through the inner air flow space 204 back to the inlet end 198 10 where the air, now further heated by radiant energy from the outer surface of inner tube 202, enters the air fed chamber 228 for further distribution through the holes 234 and into the burner 214. The ratio of air flowing into and through the respective portions of the burner is defined by the respective areas of the holes 234 into those 15 areas. As best shown in Figure 3, the number of holes 234 and cross sectional area of each hole is chosen, in one preferred embodiment, so that holes 234 in the second air feed plate 236 and side wall of the inner fire tube 216 comprise 50% of the hole area, which feeds the first fire zone 250, and the holes in the air feed plate feeding the space between the inner 20 fire tube 216 and the inlet end of the central tube 202 constitutes the remaining 50% distributed so that 25% of the open area is in the holes 234 in the air feed plate over the space between the inner fire tube 216 and the middle or central fire tube 218, feeding the second fire zone 252, 12.5% % of the open area is through the holes 234 into the space between the 25 middle fire tube 218 and the outer fire tube 220, feeding the third fire zone 254, and the remaining 12.5% of the open area is through the holes 234 into the space between the outer fire tube 220 and the inner tube 202, feeding the fourth fire zone 256. Accordingly, a defined amount of fuel is fed through the fuel nozzle 30 218 directly into the first fire zone 250. A stoichiometric amount of air, or a slight excess, at the desired combustion pressure, and having an elevated WO 99/46484 PCT/US99/05271 16 temperature heat generated as a result of compression and, if desired, countercurrent heat exchange with hot gases exiting the combustor, is fed into the closed spaced 230. The air flows through the outer air flow space 208 and the inner air flow space 204 where it picks up further heat radiated 5 from the inner tube 202 once combustion is initiated. This now further heated air is distributed through the holes so that the fuel is burned with oxygen in 50% of the air feed which enters the first fire zone 250. As the oxygen starved flame enters the second fire zone 252 an additional amount of oxygen in the next 25% of the air is consumed; likewise, oxygen in the 10 next 12.5% of the air is consumed by the flame in the third zone 254 and the oxygen in the remaining 12.5% of the air is consumed in the fourth fire zone 256, resulting in full, stoichiometric combustion entering the equilibra tion chamber 258. The temperature of the flame and combustion chamber temperature 15 profile is monitored through thermocouples, or other temperature sensory 260 located throughout the combustor. The locations of the temperature sensors 260 in Fig. 2 are merely representative and may be in various different locations in the center and on the walls of the tubes as required. In order to control the temperature of the flame and the temperature 20 profile in the combustion chamber liquid water (not steam) is injected through water nozzles 201 into the combustor at several locations. Figures 2 and 3 show several water nozzles 201 which are used to transfer the liquid water from the exterior of the combustor into the equilibration cham ber 258 of the combustor. As best shown in Fig 2, several sets of water 25 nozzles 201 are placed along the length of the combustor. In a preferred embodiment at least three sets of nozzles 270, 272, 274 are used and each set includes three nozzles 201 with the three nozzles 201 being only in less than about 1800 of the circumference and at least two of the sets being in a different 1800 of the circumference to cause a mixing flow, and possibly 30 a vortex flow, in the working fluid passing along the length of the equilibra tion chamber 258. While the nozzles are shown to be radial to the combus- WO 99/46484 PCT/US99/05271 17 tor inner tube 202, to create more turbulence as the water enters the equilibrium chamber, flashes to steam and expands, the nozzles may be placed at any number of different angles to the central axis of the combus tor to create more tangential flow or to direct the injected material down 5 stream. The water control 40, in coordination with control valves (not shown) on each of the nozzles 201 or each set of nozzles 270, 272, 274 controls the amount and location of water introduced through the respec tive nozzles 201 into the equilibration chamber 258 and, in turn the temper ature at specific spots in the chamber 258 and the temperature profile 10 therein. Under normal operating conditions less than all of the nozzles 201 may be injecting water at any time. Fig 2 also shows at least one water nozzle 201 for providing water to the air feed chamber 228 to add steam to the air prior to said air being reacted with the fuel. Further, additional nozzles may feed water into the inner or outer air flow space 204, 208. 15 The ultimate objective, which has been demonstrated by actually operation of the combustor is to limit the temperature in the equilibration chamber 258 and the fire zones 250, 252, 254, 256 to not greater than about 2200'F to 2600oF thus preventing or significantly limiting the formation of

NO

x while providing sufficient residence time at above about 18000F to 20 allow complete conversion of the burning fuel to CO 2 . Additionally, more water nozzles may be added further down stream as desired to add addi tional water if, for example it is desired to feed a steam turbine rather then a gas turbine or the ultimate objective is to produce large quantities of high pressure, high temperature steam. In such instances, water to fuel ratios as 25 high as 16 to 1 have been demonstrated without effecting the flame stability or generating pollutants. While the fuel injected into the combustor will spontaneously ignite once the internal components of the combustor are hot, it is initially neces sary, when starting a cold combustor, to provide a ignition spark to initiate 30 the flame. This is provided by igniter 262 located in the first fire zone 250. Figure 3 shows two igniters 262. However, it has been shown that a single WO 99/46484 PCT/US99/05271 18 igniter is adequate. The igniter 262 is typically a spark plug such as is used in high temperature aircraft engines. However, a glow plug, resistance heated high temperature metal rod or a spark ignited hydrogen flame are also suitable to institute ignition. One skilled in the art will readily identify 5 alternative igniters. The multiple tube construction of the combustor provides a unique benefit regarding the mechanical stress applied across the central tube 202 during operation. In the preferred embodiment discussed above, the working fluid in the space within the inner tube 202 (the equilibration 10 chamber 258) is at elevated temperatures, possibly as high as 2600oF, and pressures from about 4 atmospheres to greater than 30 atmospheres. Generally, if a means were not provided to lower the temperature of the wall of inner tube 202 or prevent the inner tube 202 from experiencing a significant differential pressure across that wall, these operating conditions 15 could damage the material used to construct the tube. However, as shown in Fig. 2, the air exiting the compressor 10 enters the outer air flow space 208 at a pressure substantially the same as the pressure within the inner tube 202. Substantially the same pressure exists within the inner air flow space 204. As a result, the central tube 202, with the exception of its 20 exhaust end 196, for all practical purpose does not have a differential pressure applied thereto. Further, the compressed air flowing through the inner air space 204 continuously sweeps across the entire outer surface of the inner tube 202, thus keeping the inner tube outer diameter at a temper ature less than that of the working fluid flowing in the equilibration chamber 25 258. The only tube exposed to the full differential pressure, i.e., the pressure difference between the internal pressure in the combustor and atmospheric pressure, is the outer tube 210 which is at the lowest tempera ture of the three tubes and is most capable of withstanding the differential pressure. This design is so effective in keeping the outer tube 210 at the 30 lowest possible temperature that if room temperature compressed air is feed WO 99/46484 PCT/US99/05271 19 to the combustor operating at a TIT of 2100F the outer tube 210 is cold to the touch during operation. The pressure ratio, turbine inlet temperature, and water inlet tempera ture can be varied as required by the application in which the VAST cycle is 5 used. Additionally, the fuel/air ratio is changed depending on the type of fuel used, to assure stoichiometric quantities, and the efficiency of systems using the combustor can be increased by use of more efficient compressor and turbine designs. Increasing the air feed while maintaining the fuel/air ratio constant results in a proportional increase in the power output. 10 The VAST cycle is a combination of a compressed air work cycle and a steam cycle since both air and steam are present as a working fluid. Each makes up a portion of the total pressure developed in the combustor. In the present discussion, it will be understood that the term working fluid is intended to include the steam generated from injected water products of the 15 fuel burned with the oxygen in the inlet compressed air together with the nonburnable air components and any excess compressed air which may be present, and thus includes all of the products of combustion, inert air components and steam. The term "steam" refers to water which is injected in the liquid state to become superheated steam. The described process 20 makes use of the combined steam, combustion products and air as a working fluid. A brief discussion of the thermodynamic processes in the VAST cycle now follows. The air is compressed in compressors, generally a two or three stage compressor, 10. The exit conditions at the outlet of compres 25 sor 10 are calculated using is entropic relations for compression and the real conditions are calculated using a compressor efficiency of 85%. As explained above, compressed air enters combustion chamber 25 through air flow control 27. The combustion chamber 25 burns fuel at constant pressure under 30 conditions also approximating constant temperature burning. The tempera ture is completely controllable since there are independent fuel, air and WO 99/46484 PCT/US99/05271 20 water controls. Compressed air input to the combustor, after start-up, is at constant pressure. Thus, the combination of the air feed at a constant pressure and a fixed fuel/air ratio in combination with control of the TIT by water injection results in a constant pressure in the combustion chamber. 5 Burning occurs in the combustor immediately following injection of fuel under high pressure and provides idealized burning conditions for efficiency and avoidance of air contaminants in which the fuel mixture may at first be richer than the mixture for complete combustion, additional air being added as burning continues, this air being added circumferentially around the 10 burning fuel and in an amount which, as a minimum, equals the amounts necessary for complete combustion (a stoichiometric amount) but can ultimately exceed that necessary for complete combustion of the fuel components. While a stoichiometric amount of air may be introduced a 5% excess appears to force complete combustion and provides excess oxygen 15 for acceleration if desired. Water at high pressure, which may be as high as 4000 psi or greater, is injected by water injection control 40. The pressure is maintained at a level to prevent vaporization prior to entering the combustor. Due to the high temperatures and lesser pressure in the combustion chamber 25, the 20 injected water is instantaneously flashed into steam and mixes with the combustion gases. The amount of water that is added into the combustion chamber 25 depends on the desired turbine inlet temperature (TIT) and the temperature of the water just prior to injection. Part of the heat released during the combustion of fuel is used to raise the temperature of the 25 unburned (inert) portion of the compressed air from the three stage com pressor 10 to the TIT. The remaining heat of combustion is used to convert the injected water into steam. Table 1 sets forth several sets of operating conditions for a system using #2 diesel fuel. For example referring to Example 30, a pressure ratio 30 of 30/1, a turbine inlet temperature of 2050'F, a turbine outlet pressure of 0.5 atmosphere and a water inlet temperature of 598oF are indicated. The WO 99/46484 PCT/US99/05271 21 results predicted by a computer simulation modeling the system projects the efficiency of the compressor and the work engine using a fairly standard published turbine efficiency of 92%. This resulted in a net horsepower of 760, an SFC of 0.31 and an efficiency of 0.431. The examples calculated 5 in Table I of a simulated process and listed in the data tables show the result of varying the pressure ratio, water inlet temperature and Turbine Inlet Temperature (TIT) held constant. In a like manner, other operating conditions can be varied. For example the water temperature can be increased, the maximum temperature 10 being not greater than the desired TIT. Preferentially, the water tempera ture is not increased to a temperature greater than about 50oF below the desired TIT. However, for practical reasons, since the working fluid exiting the turbine is used to heat the feed water, the inlet water is usually held to no more than about 50oF below the turbine exit temperature. The higher 15 the water temperature the greater the quantity of water necessary to reduce the combustion temperature to the TIT, thus resulting in a greater mass of gases flowing to the turbine and a greater power output. Likewise the TIT can be raised or lowered. Examples 1-7 in the data table were calculated at a TIT equal to 1800'F. This is the generally accepted maxi 20 mum for turbines which do not utilize high temperature alloys or hollow blade cooling with either air or steam. However, utilization of high tempera ture and/or corrosion resistant alloys, high temperature composites, ceram ics and other materials designed for high temperature operation, such as used in turbine jet engines will allow operation at 2300oF or higher. 25 Examples 8-13, 15-31, and 14 illustrate operation at more elevated temper atures, namely 2000'F, 2050oF and 2175oF respectively. Examples 1-5 of Table 1 show the effect on horsepower, efficiency and SFC by increasing the air compression ratio. The effect of reducing the exit pressure (calculated at a turbine efficiency and compressor efficiency of 30 85%) is shown in Examples 2, 6 and 7. Examples 8-13 show the effect of air compression ratio on a system with a TIT of 2000oF, a turbine exit WO 99/46484 PCT/US99/05271 22 pressure of 0.5 atmosphere and a H 2 0 inlet temperature of about 595 to about 700'F when calculated at an assumed turbine efficiency of 90%. It should be noted that a turbine efficiency of 93% is claimed by currently available air compression axial turbines and the power turbine expander 5 train. Examples 15-24 and 25-31 further demonstrate the effect of increas ing air pressure at two different turbine efficiencies. In examples 1 through 31, the fuel is diesel #2 and the fuel to air ratio is 0.066, which is the stoichiometric ratio for #2 diesel fuel. With 10 other fuels a different f/a ratio is required to maintain stoichiometric condi tions. Example 32 uses methane and a f/a = 0.058. Because methane burns more efficiently than diesel fuel, less fuel per pound of air is used and, as a result, less water is added.

WO 99/46484 PCT/US99/05271 23 O' LO a) mm0o 00 r% 0 I 0o ) c) cO cO cO) Lo (D 0D R" LL ~ ~ Y Y Y ) C O > Na ) O ) CY) 0 NO u O O OO O O o o N 0 O o_ .0 O N 0t N 't CY) O 0 LO CO O) CO m - N4 N N O - CO 1 e Om e" O m e O O uI 00 00 N- N CO 0 a, m ma a)

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-1~~ E 0 0 0 0 C,4 LO) L)L . 10 U HOR oE m0 -oR SUBTIU N NHE NRL N26NN) WO 99/46484 PCT/US99/05271 27 Example 32 is also calculated at a turbine efficiency of 93%, and a turbine inlet temperature of 2175'F which are both claimed as operating parameters of commercially available turbines (which do not use the claimed invention.) 5 The effect of changing air compression ratio on the closed cycle performance of the systems listed in examples 8-13, 15-20 and 25-30 are plotted on Figures 7-10. In particular Fig. 6 shows thermal efficiency, Fig. 7 shows SFC, Fig. 8 shows turbine power and Fig. 9 shows net power. The combustor of the invention differs from prior devices in a funda 10 mental respect since the working fluid mass may be increased either at constant pressure, constant temperature or both. Constant temperature is maintained by combustion controller 100 through controlled water injection by water injection control 40 in response to temperature monitors (thermo stats) in combustor 25. Within combustor 25, typical combustion tempera 15 tures for liquid hydrocarbon fuels reach about 3,0000 to 3,800oF when a stoichiometric amount or a small excess of compressed air is supplied by compressor 10. Larger quantities of excess air reduce the resulting turbine inlet temperature but would not greatly affect the actual temperature of burning or the ignition temperature. 20 The practical limit of the discharge temperature from the combustor 25 is in turn governed by the material strength of the containing walls at the discharge temperature, the high temperature tolerance of the combustor walls, the materials of construction of the power turbine, and whether the turbine blades are separately cooled, either externally or internally. This 25 discharge temperature is controlled between suitable limits by variation in the injection of high pressure water which then flashes to steam, the heat of the vaporization and superheat being equated to the heat of combustion of the fuel being burned. (The temperature of the burning fuel is reduced to the desired TIT primarily if not totally by the heat of vaporization and 30 superheat as the water vaporizes and then heats up to the TIT). The WO 99/46484 PCT/US99/05271 28 quantity of injected water is thus determined by the desired operating temperature, being less for high superheats, but actually maintaining a fixed operating temperature. The working pressure is kept constant by compressor 10 as required 5 by any desired engine rpm. The resulting working fluid mixture of combustion gases unreacted components of air (i.e. N 2 , C0 2 ) and steam is then passed into a working engine 50 (typically a turbine as explained above) where expansion of the steam - gas mixture takes place. The exit conditions at the outlet of 10 working engine 50 are calculated using isentropic relations and turbine efficiency. The exhaust gases and steam from work engine 50 are then passed through an exhaust control 60. Exhaust control 60 includes a condenser where the temperature is reduced to the saturation temperature correspond 15 ing to the partial pressure of steam in the exhaust. The steam in the turbine exhaust is thus condensed and may be pumped back into the combustion chamber 25 by water injection control 40. The remaining combustion gases are then passed through a secondary compressor where the pressure is raised back to the atmospheric pressure if a vacuum was 20 pulled on the exit of the turbine so that it can be exhausted into the atmo sphere. Alternatively, the exhaust from the turbine, which is a superheated steam stream, can be used directly, as will be recognized by those skilled in the art. It can be seen that the present invention takes substantial advantage 25 of the latent heat of vaporization of water. When water is injected into a combustion chamber, and steam is created, several useful results occur: (1) the steam assumes its own partial pressure; (2) the total pressure in the combustor will be the pressure of the combustion chamber as maintained by the air compressor; (3) the steam pressure is without mechanical cost, 30 except a small amount to pump in the water at pressure; (4) the steam WO 99/46484 PCT/US99/05271 29 pressure at high levels is obtained without mechanical compression, except the water, with steam at constant entropy and enthalpy. The water conversion to steam also cools the combustion gases, resulting in the pollution control described below. 5 B. Pollution and Efficiency Control Any type of combustion tends to produce products which react in air to form smog, whether in engines or industrial furnaces, although of different kinds. The present invention reduces or eliminates the formation of pollution products in several ways discussed below. 10 First, internal combustion engines operated with cooled cylinder walls and heads have boundary layer cooling of fuel-air mixtures sufficient to result in small percentages of unburned hydrocarbons emitted during the exhaust stroke. The present invention avoids combustion chamber wall cooling in two distinct ways to keep the burning temperature for the fuel at 15 a suitable level, both of which are shown in more detail in U.S. Patent No. 3,651,641. First, hot compressed air is made to flow by air flow control 27 around an exterior wall of combustor 25 such that combustion occurs only within a small space heated above ignition temperatures. Second, the combustion flame is shielded with air unmixed with fuel. Thus, a hot wall 20 combustion, preferably above 2000'F, is utilized in an engine operating on the present cycle. Next, smog products are also inhibited by operating the combustor 25 within a defined temperature range. For example, CO and other prod ucts of partial combustion are reduced by high temperature burning, prefera 25 bly well above 2000 0 F, and by retaining such products for a considerable dwell time after start of burning. At too high a temperature, however, more nitrous and nitric oxides (NOx) are formed. Accordingly, neither extremely high nor extremely low temperatures are acceptable for reducing smog products. The combustion controller 100 in the present invention com- WO 99/46484 PCT/US99/05271 30 mences burning of the fuel and air at a controlled low temperature by the staged burning in the burner 214, then increasing progressively for a considerable dwell time and then cools (after completion of the burning) to a predefined, smog-inhibiting temperature (TIT) by the use of water injec 5 tion. Thus, combustion is first performed in a rich mixture; then sufficient compressed air is added to allow complete combustion of the fuel with a minimum of excess oxygen and to cool the gases below about 2500oF for about half of the dwell time in the combustion chamber 25. Water injection is directly added to the burner, combustion chamber or upstream by water 10 injection control 40 to maintain an acceptable temperature preferably in the range of about 2500'F that assures complete burning of all the hydrocar bons before cooling to the desired TIT. In typical engines, hydrocarbon fuels are often burned in a mixture with air a little richer in fuel, i.e., at less than stoichiometric proportions in 15 order to increase efficiency. This, however, results in excess CO and more complex products of incomplete combustion. The present invention, however, because it provides a progressive supply of air through air flow control 27, dilutes the combustion and further reduces such smog products. Oxides of nitrogen also form more rapidly at higher temperatures as 20 explained above, but can also be reduced by the controlled dilution of the combustion products with additional compressed air. The present combustion cycle is compatible with complete and efficient fuel burning and eliminates incomplete combustion products and reduces other combustion products such as nitrogen oxides. Combustion 25 controller 100 allows burning of the combustion products at a considerable initial dwell time, after which the products of combustion and excess air are then cooled to an acceptable engine working temperature, which may be in the range of 1000°F to 1800oF, or even as high as 2300OF if proper materials of construction are used in the turbine, or may be as low as 30 700oF to 800oF.

WO 99/46484 PCT/US99/05271 31 An equilibrium condition can be created by making combustion chamber 25 at least about two to four times the length of the burning zone within combustion chamber 25; however, any properly designed combus tion chamber may be used. 5 A burning as described provides a method of reducing smog-forming elements while at the same time, providing a complete conversion of fuel energy to fluid energy. The VAST cycle is a low pollution combustion system because the fuel-air ratio and flame temperature are controlled independently. The 10 control of fuel-air ratio, particularly the opportunity to burn all of the oxygen in the compressed air (or to dilute with large amounts of compressed air, if desired) inhibits the occurrence of unburned hydrocarbon and carbon monoxide resulting from incomplete combustion. The use of an inert diluent (water) rather than air permits control of the formation of oxides of nitrogen 15 and represses the formation of carbon monoxide formed by the dissociation of carbon dioxide at high temperature. The use of diluents of high specific heat, such as water or steam, as explained above, reduces the quantity of diluent required for temperature control. In the case of oxides of nitrogen, it should be noted that the VAST cycle inhibits their formation rather than, 20 as is true in some systems, allowing them to form and then attempting the difficult task of removing them. The net result of all of these factors is that the VAST cycle operates under a wide range of conditions with negligi ble pollution levels, often below the limits of detection for hydrocarbons and oxides of nitrogen using mass spectroscopic techniques. 25 Others have attempted to inject small amounts of water but they have done so under conditions not conducive to, or incompatible with, operation at zero pollution resulting in reducing efficiency. Kidd U. S. Patent 4,733,527 refers to the injection of relatively small amounts of water into the combustion chamber at the same time as the fuel 30 and apparently into the flame itself, thus reducing the temperature of the WO 99/46484 PCT/US99/05271 32 flame in an attempt to reduce NOx formation. However, Kidd, as well as other persons skilled in the art, have been unable to obtain significant reduction of, or prevent the formation of, NOx. The best NOx levels that have been demonstrated by others on a combustor, without catalytic 5 converters, is about 25 to 30 ppm. Kidd demonstrates the best known prior art with control and reduction of NO x levels to no less than 30 ppm by adding water in amounts equal to or less than the amount of fuel, ie WFR= 1.0. In contrast thereto applicant has actually demonstrated NOx levels as 10 low as 4 ppm with a WFR of 5.57 when the compressed air inlet tempera ture was approximately 4000F. This is more fully set forth below. If the air temperature had been 9640 F, which is the standard exhaust temperature from a 2 stage compressor at 30:1, the WFR would have been 8.27. The ability to deliver such large amounts of water is a result of operating a 15 unique combustor, at conditions which everyone in the past has said are inoperable and at which those skilled in the art have said that unacceptable low temperatures would be created, combustion flame would be extin guished, and the operating efficiency would render the equipment unusable as a power source for a work engine. Contrary to the prior art which 20 operated to lower the flame temperature on a system already using large amounts of air to control temperatures, applicant generates a controlled hot flame with a stoichiometric amount of air and then rapidly cools the com bustion products to produce the desired exhaust composition. Substantially all of the cooling of the working fluid and/or the com 25 bustion temperature and the exit temperature (the exit from the combustor or turbine inlet temperature) is provided by the latent heat of vaporization of the injected liquid, such as liquid water. The result is that the fuel/ air mixture can be selected so that the most efficient flame from the stand point of combustion, combustion products and heat generation can be 30 selected and operation is not constrained by the need, as in prior art de- WO 99/46484 PCT/US99/05271 33 vices, to provide considerable excess air for cooling the combustion prod ucts. Further, prior art devices, controlled pollutants by limiting the flame temperature. In contrast thereto the present invention allows a stoichiomet ric mixture (or near stoichiometric) of air and fuel to be used to produce a 5 hot staged flame with complete combustion to eliminate CO residuals, followed by controlled cooling and mixing of the combustion products to the desired TIT, the combination preventing the formation of NOx. Further, one skilled in the art knows that the amount of power produced by a power turbine depends on the temperature and the mass of 10 the working fluid entering the turbine and the pressure difference across the turbine. When a hot, efficient flame is produced by providing a stoichiomet ric mixture of fuel and air (generally above 2300 0 F) and substantially all cooling is provided by the latent heat of vaporization of liquid water injected into the combustion chamber, the injected liquid being used to reduce the 15 exit temperature of the working fluid, to the maximum TIT for a state of the art gas turbines (1850'F to about 2100F) the amount of water is from about 5 to about 8 times the weight of fuel used, depending on the flame temperature and the temperature of the compressed air and water entering the combustor. For a specific flame, water, and air inlet temperature, the 20 quantity of water supplied can be precisely determined for a desired TIT. While the gas turbine will operate in a highly efficient manner when the TIT of the working fluid in the 1850 - 21000 range, efficiency can be improved by using a higher TIT. The current limiting factor is the materials of con struction of state of art turbines. Increasing the mass of the working fluid 25 entering the turbine while lowering its temperature by injecting high vol umes of water to produce the preferred TIT significantly increases the efficiency of electrical energy production by the turbine. This is accom plished by use of applicant's invention wherein the excess air is substan tially eliminated resulting in a hot flame. Rapid cooling to the preferred TIT 30 by water injection results in improved efficiency for the production of useful WO 99/46484 PCT/US99/05271 34 energy while at the same time preventing the formation of undesirable pollutants such as NO and NO 2 due to the almost complete elimination of excess 02 available for nitrogen oxidation. Table 1 of the specification lists selected operating conditions and 5 results generated for 32 different operating conditions. In all instances the efficiency is higher than, and the specific fuel consumption is less than, prior art engines, operating with the same amount of fuel. Table 2, Exam ples 33-40 show simulation results of Brayton cycle engines operating with the same amount of air at an A/F = .02020. Computer simulation has 10 shown that the claimed engine will operate 10% more efficiently, and the fuel consumption will be 10% less than engines operating without the claimed invention. Actual operation of a combustor under conditions produced a working fluid with NOx and CO below 1 ppm and no unburned fuel (HC). 99-100% 15 combustion efficiency was obtained. The combustor operated in a stable manner (no evidence of flame instability or temperature fluctuation) with water/fuel ratios used for the examples set forth in Table 3. Table 3 sets forth data obtained for a VAST Combustor fabricated and operated in the manner described herein using diesel #2 as the fuel and 20 under conditions set forth in Example 3, 13, 20 and 30, with the exception that the exit pressure was 1.0 atmosphere.

WO 99/46484 PCT/US99/05271 35 0 N () CD LO -. Y ) It a) UO Nt (0 N (D0(D 00 ItU) () -0 - 0U M ) CO) co 0 co 0 0 w- '- U t It r- N Y '-o 0 CY) ' 0 - 0U LO 0) CY) r- 0' 0 0 (0 ~ ~ C1 0

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% 0 C '- ) N U) u) N 0) U) U) Y) 0 C Lo 0 M- U 0 N U) 0'- '-0N LU N m~ '0 - 0U NO) N, a, a 0 LO O D CY 00-U )L '-) U) 0~ CO ) CV) IU)Y)Ic l 0 0) L LO0 C co ' 0 '-CU 0-0 0 ~ COO m C'-0 U) CC) 0) LO T)NO U N )N V 6 0- ~ N~ rj- 00 0 0, mY U-0'- 0U if-0 R. N N <N N W: - N ww 0 - o WO 99/46484 PCT/US99/05271 36 The exhaust gas was analyzed using an Enerac 2000, provided by Energy Efficient Systems, calibrated for 02, NOx, CO and combustibles (unburned fuel) by the supplier. The Enerac 2000 was then connected by copper tubing to a test port located at the TIT position in the combustor. 5 Listed in Table 3 are various operating parameters and gas composi tion readings. The values given for fuel, air and water are in pounds per second. TIT corresponds to the turbine inlet temperature. Also included are calculations of the air/fuel ratio and water/fuel ratio. The 7 lines on the bottom half of Table 3 reflect values measured by 10 the Enerac 2000 (NOx, CO, 02, combustibles) and calculated values for burning efficiency, CO2 and excess air. The manufacturer of the Enerac 2000 has indicated that the burning efficiency is artificial low because the particular unit used is an older unit which does not have a correction in the algorithm for measurement at ambient temperature rather than recom 15 mended temperature of 200oF. The actual values of burning efficiency rather than being from 94.4 to 96.4 are closer to 100%. The manufacturer of the test equipment has indicated that the measured values are much more reliable and that the readings of unburned fuels indicate 99-100% combustion efficiency. 20 Depending on operating conditions in each test run, NOx was below 9ppm and CO was undetectable with recorded NOx levels as low as 4 ppm and observed readings on the digital readout of the test unit for other data points as low as 3 ppm. While the water/fuel ratio for the illustrated test run was from 4.75 25 to 6.88, water to fuel ratios as high as 9.36 were recorded without effect ing the stable operation of the combustor. Further, input air was approxi mately 400-500oF. When the input temperature is greater than 900'F, which is the typical temperature for a two stage compressor with a 30 atmosphere exit pressure, at least an additional two pounds of water per WO 99/46484 PCT/US99/05271 37 pound of fuel is required to maintain the flame temperature in the desired range. The exhaust gases exiting the combustor, when operated under the conditions listed in Table 3 hereto with indication of 0 ppm of CO, when 5 visibly observed, were completely clear and transparent with no observable smoke, steam or particulate material. Aside from visual distortion due to the heat of the exhaust stream, there was absolutely no visible indication that diesel #2 fuel was being burned. The combustor 25 represents a mechanism for using heat and water 10 to create a high temperature working fluid without the inefficiencies that result when, in order to generate steam the heat is transmitted through a heat exchanger to a flash vaporizer or a boiler. The addition of water rather than merely heated gas to the products of combustion represents a means for using a fluid source for producing the gas, the water flashing to steam 15 providing a very efficient source of mass and pressure and at the same time giving tremendous flexibility in terms of temperature, volume, and the other factors which can be controlled independently. In addition, injected water, when added directly into the combustion chamber to quench the combus tion process, greatly reduces contamination that results from most combus 20 tion processes. Further, the amount of nitrogen available to form No x is significantly reduced. Only about 30% as much nitrogen is in the combusted gases of the combustion chamber 25 compared to a normal air dilution open cycle Brayton engine of any form or model because water rather than excess air 25 is used for cooling and the amount of air fed to the system is thus greatly reduced. In particular, about 1/3 as much air is fed to the combustor. As discussed below this also significantly reduces the energy expended on compressing the feed air. Further, the injected water rapidly expands as it flashes to steam, the 30 volume increase at 30 atmosphere being greater than 50/1.

WO 99/46484 PCT/US99/05271 38 C. Water Injection Water injection control 40 controls the pressure and volume of water 41 injected through nozzles 201, arranged for spraying a fine mist of water in the chamber. Water may be injected into the combustor in one or more 5 areas, including: atomized into intake air before compressor 10, sprayed into the compressed air stream generated by compressor 10, atomized around or within the fuel nozzle or a multiplicity of fuel nozzles, atomized into the combustion flame in combustion chamber 25, or into the combus tion gases at any desired location, or downstream into the combustion 10 gases prior to their passage into work engine 50. Other areas of injection can be readily envisioned by the skilled artisan. As described earlier, the amount of water injected is based on the temperature of the combustion products and the desired maximum temperature and temperature profile in the equilibration zone 258 as monitored by temperature sensors 260 in 15 combustor 25. The amount of water injected is also dependent on the system using the VAST cycle. For example, if the water is recycled as for use in a motor vehicle, the water is cooled as much as possible to obtain a usable balance between total water used and power output, i.e., if the inlet water temperature is low and the TIT is high a small volume of water can 20 be used to reduce the combustion temperature to the TIT. On the other hand, if a major purpose of the system is to produce potable water from polluted or salt water, as discussed below, while generating electrical energy, the water inlet temperature would be raised as high as possible while the TIT is lowered. 25 D. Increased Available Power Using the VAST system with water injection, a stoichiometric amount of air, or a slight excess of air, is fed. The amount of air fed is significantly reduced, when compared with a system burning the same quantity of fuel operating according to the Brayton cycle (no water injec- WO 99/46484 PCT/US99/05271 39 tion, cooling provided by excess air). The VAST system thus requires a much smaller compressor then in a Brayton cycle combustor and, accord ingly, that portion of the energy generated by the turbine which is used to drive the compressor is significantly reduced. For example, if about one 5 third of the Brayton cycle quantity of the air is used a smaller compressor with about one-third the power requirements can be used. The energy which would have gone to power the larger compressor is instead now available as additional energy for supplying the customer or run additional equipment. 10 Examples 33 - 40 list calculated values for a power system operating under the Brayton cycle. This data can be compared with Examples 25 - 31 operating (at 1 #/sec air) under the same conditions according to the VAST system. Off particular relevance is the significant difference in the available turbine horsepower, a significant additional amount being available from a 15 system operating with the VAST combustor. More specifically, using the fuel requirements from the NACA tables for diesel #2, the Brayton cycle requires 0.0202 Ibs/ sec of diesel #2 for each pound of air. However, stoichiometric requirement (no excess air, all fuel and oxygen consumed) are 0.066 pounds of diesel per pound of air. In 20 other words, when 0.0202 Ibs of diesel are burned the oxygen in only 0.306 pounds of air are consumed. For equal quantities of fuel, namely 0.066 lbs of diesel, VAST consumes 1 pound of air while a Brayton cycle system utilizes 3.27 pounds of air. However, the VAST combustor requires 0.5463 pounds of water when operating at a TIT 2050'F for a total mass 25 flow to the turbine of 1.6123 pounds compared to 3.336 pounds for the Brayton cycle. Since the power output of the turbine depends on the mass fed to the turbine, In order for the turbine to generate the same amount of energy, the VAST combustor requires the total mass to be approximately doubled (2.07 times) increasing all of the feed components proportionally 30 and the amount of air to 2.07 pounds. Comparing this to the 3.27 pounds WO 99/46484 PCT/US99/05271 40 required with Brayton, 1.2 pounds less air is required, a compressor of 63.3% of the size of the Brayton cycle is used and the energy needed to drive the compressor to supply the required air is reduced by 36.7%. Diesel #2 releases 1936BTU/pound when fully combusted. It can then be calcu 5 lated that 0.066 pounds of Diesel #2 when combusted generates 1808 combusted horsepower. Example 30, operating at 43.1% efficiency generates 766hp. While Brayton operates at a lesser efficiency, assuming it operates at the same efficiency, the balance of the combusted horsepower is required to drive the compressor. Therefore, the compressor to deliver 10 3.27 pounds of air require 1042hp or 318.65hp per pound of air. There fore, for the same amount of fuel, it can be calculated that about additional 723 hp is available as additional available shaft energy. Another way of comparing the systems, if a current single shaft compressor turbine were operated and the VAST combustor were used to 15 replace the combustor operating under the Brayton cycle sufficient mass is generated to drive the turbine in the same manner as in the past. However, because additional fuel must be burned to consume all the delivered oxygen and additional water added to control the temperature of that additional burned fuel sufficient excess mass is generated at the desired TIT to drive a 20 second turbine at least about 50% in size of the first turbine, or a signifi cant amount of additional higher temperature, high pressure steam is available for other power applications. D. Other Embodiments Of Present Invention 1. Power Plant Including Water Purification 25 In the case of electric power generation using sea water, brackish water, or polluted ground water or well water as a coolant, the cycle may be open as to electric power, and the water used as shown in Figures 4 and 5. Feed water 41, moved by pump 42, is heated as it passes through condenser 62 and heat exchanger 63 countercurrent to exiting hot working WO 99/46484 PCT/US99/05271 41 fluid 51 and is flash vaporized in the combustor 25 or 200 as described above. By increasing the diameter of the combustion chamber the velocity of the working fluid can also be reduced thus allowing easier removal of water bourn materials or solutes. 5 The typical temperature of operation of the combustor is 1500oF to 2300 0 F. When salt water or brackish water is the feed source this temper ature is above the melting point but significantly below the boiling point of the salts in sea water (85% of sea salt is NaCI; an additional 14% is composed of MgCI 2 , MgSO 4 , CaCI 2 and KCI). When the water flashes to 10 steam the dissolved inorganic contaminants rain out as a liquid and organic contaminants are combusted. For example, NaCI melts at 1473 0 F and boils at 2575 0 F, the other salts have lower melting points and higher boiling points. As a result the molten salts are readily collected along the bottom wall of the combustor and the liquid salts can be removed by a screw 15 assembly on the bottom of the combustor, fed through an extruder and die where it can be formed into rods or pellets, or sprayed through nozzles, using the pressure in the combustor as the driving force, into a cooling chamber where the waste material can be deposited in a waste collection container 80 as flakes, powder, or pellets of any desired size or shape by 20 selection of the proper spray nozzle dimensions and configuration. Because the salt water is exposed to extremely high temperatures in the combustion chamber the salt recovered is sterile and free of organic matter. Water on the order of 6 to 12 times fuel by weight is atomized into the combustion flame and vaporized in milliseconds. Salt or impurities 25 entrained in the steam are separated from steam and then crystallized, precipitated and/or filtered leaving behind clean steam. Salt or waste collection and removal mechanism 80 can be accom plished by any of a number of well-known means from combustion chamber 25, such as by a rotary longitudinal auger. This auger is sealed so as not to 30 bypass much pressurized working gases as it rotates and removes the WO 99/46484 PCT/US99/05271 42 precipitated salt. As mentioned above, an alternative is to spray the molten waste or salt through spray nozzles into a collecting tower or extrude the salt 81 into strands or rods which can then be cut to desired sizes. A still further alternative is to drain the molten salt directly into molds to form salt 5 blocks 81 which are then easy to transport and use in chemical processing reprocessed for recovery or otherwise disposed of. The resulting working fluid, which now includes clean water steam, may be fed into one or more standard steam or gas turbines. Following work production by the expanding steam-gas mixture, a condenser 62 10 condenses steam 61 resulting in a source of usable potable water 65. Using this open cycle at pressure ratios of from 10:1 to 50:1 or higher electric power may be generated at good efficiencies and specific fuel consumption. Figure 6 shows a second embodiment of a unit using the VAST 15 cycle. In this embodiment, the efficiency of the system is further increased by capturing additional waste heat from the combustion chamber 25. The combustion chamber 25 is enclosed in a double shell heat exchanger 90. In the version shown, the hot compressed air 11 exiting the compressor 10 passes through the shell 92 immediately surrounding the combustion 20 chamber 25 before it enters the combustor 25. The cold water 41 is fed to a second shell 94 which surrounds the first shell 92. In this manner the air 11 absorbs additional heat normally lost from the combustor 25 and the incoming water 41 absorbs some of the heat from the compressed air 11. An additional benefit, since the air 11 is at an elevated pressure, is that the 25 pressure differential across the combustion chamber 25 wall (i.e. the difference between the combustor interior and ambient conditions as in Figure 5 or the difference between the combustor interior and the com pressed air 11 is significantly reduced, thus reducing the stress on the combustor wall from the combination of high temperature and high pres 30 sure. The water 41, after passing through the combustion chamber outer WO 99/46484 PCT/US99/05271 43 shell 94, then proceeds through the condenser 62 and the heat exchanger 73 to acquire the desired injection temperature. Care is taken to maintain the water under pressure possibly as high as 4000 psi so that, as the water is heated, it does not convert to steam before it is injected into the combus 5 tion chamber 25 which is at a higher temperature and, in most instances, a lower pressure than the superheated water 41. Purification of contaminated waste products or treatment of solid, liquid and gaseous waste products from commercial processes resulting in useable products with power production as a by-product are also potential 10 applications of an engine employing the VAST cycle. Waste water from dried solid waste products may be used in the present invention, resulting in filtered, useable water as one byproduct. The combustible materials are additional fuel for burning in the combustor 25 and the inorganic dried waste products may then be used to create fertilizers. As is apparent, other 15 chemicals can be extracted from solid and liquid products using the present invention. Sewage treatment is also an application. Other applications include water softening, steam source in conjunction with oil field drilling operations and well production, recovery and recycling of irrigation water along with fertilizer and minerals leached from the soil, municipal solid 20 waste, etc. 2. Aircraft Engines The VAST cycle described about, particularly when operated with recycled water, is particularly efficient and has a relatively low fuel con sumption when used in commercial aircraft which normally operates at 25 30,000 to 40,000 feet. At such elevations ambient pressure is 0.1 to 0.25 atmospheres or lower and ambient temperature is well below 0OF. Exam ples 5-7 open cycle data illustrate the benefit of lowering turbine exit pressure. To generate turbine exit pressures below atmosphere, such as when operating the system at sea level, a vacuum pump on the turbine exit WO 99/46484 PCT/US99/05271 44 is necessary. This pump, which consumes energy generated by the sys tem, reduces the usable energy and efficiency of the system. Elimination of the turbine exit vacuum pump by operating in an environment with pressures less that atmosphere, such as at elevations 5 greater than about 30,000 feet, increases the usable power output of the system, and therefore, reduces fuel consumption. Further, if the water in the system is to be recycled, the ambient air temperature can be used to condense and cool the exiting gas stream and separate the water for recycling reducing the amount of energy used to recover the heat. 10 3. Steam Generation and Steam/Power Cogeneration It is also contemplated that the combustor and its control system, along with a suitable compressor can be used without the power turbine solely for the generation of high temperature, high pressure steam, the generation of potable water, or the recovery of valuable inorganic materials 15 dissolved in the water. Alternatively, one or more gas and/or steam tur bines sized to produce a desired amount of electrical energy can be coupled to the combustor to deliver electrical energy as well a mix of high tempera ture, high temperature steam as a side stream directly from the combustor. While various embodiments of the present invention have been 20 shown for illustrative purposes, the scope of protection of the present invention is limited only in accordance with the following claims and the spirit and scope of the appended claims should not be limited to the descrip tion of the preferred versions contained herein.

Claims (16)

1. 45

   What is claimed is: 1 . A power generating system comprising a) a combustion chamber, b) a work engine coupled to the combustion chamber, c) fuel supply means for delivering fuel to the combustion chamber, d) air supply means for delivering compressed air at an elevated temperature and at a constant pressure to the combustion chamber the amount of air being chosen so that at least about 90% of the oxygen in the air is consumed when burned with the fuel, the fuel and air being mixed in the combustion chamber, e) control means to vary the quantity of air supplied to the combustion chamber and to adjust the amount of fuel supplied to the combustion chamber so that the fuel to air ratio remains constant, f) a fuel igniter for igniting the mixture of fuel and air to produce a combustion vapor stream, g) liquid supply means for delivering superheated non- flammable liquid under pressure to the combustion chamber, the liquid being converted substantially instantaneously upon entering the combustion chamber to a vapor, the delivery and formation of vapor creating turbulence and mixing in the combustion chamber resulting in a working fluid composed of vapor, combustion products and non- flammable materials in the air and fuel, said working fluid being delivered to the work engine, h) a combustion chamber temperature controller, said controller delivering the superheated non-flammable liquid to the combustion chamber in quantities sufficient to maintain the tempera- ture of the working fluid at a desired level, substantially all of the control of the temperature in the combustion chamber being derived 46 from the latent heat of vaporization of the non-flammable liquid introduced into the combustion chamber, and i) heat exchanging means for transferring heat from the working fluid exiting the work engine to the nonflammable liquid, said heat elevating the temperature of the non-flammable liquid from a feed temperature to the desired temperature for delivery to the combustion chamber.
2. 2. The process of claim 1 also including the step of delivering additional non-flammable liquid to the compressed air prior to introduction of the compressed air into the combustion chamber.
3. 3. The process of claim 1 wherein the compressed air is mixed with the fuel in at least two stages such that a portion of the air is mixed with the fuel, the fuel is ignited and then the remainder of the air is added to the fuel at a point downstream of the fuel igniter.
4. 4. The process of claim 3 wherein about 50% of the compressed air is mixed with the fuel in a first zone of a burner at one end of the combustion chamber, said mixture of air and fuel is ignited to produce a fuel rich flame, about 25% of the air is added to fuel rich flame in a second zone of the burner located down stream from the first zone, about 1 2.5% of the air is added to the flame in a third zone of the burner located down stream from the second zone, and the remainder of the air is added to the flame in a fourth zone of the burner located down stream from the third zone.
5. 5. The process of claim 4 wherein controlled amounts of the non- flammable are injected into the combustion chamber at multiple locations in the combustion chamber downstream from the fourth zone of the burner.
6. 47 6. The process of claim 4 wherein controlled amounts of the non- flammable liquid are also injected into the compressed air prior to mixing of the air with the fuel.
7. 7. The process of claim 3 wherein, prior to mixing the air with the fuel, the compressed air is heated by heat radiating from the combustion chamber by passing said compressed air through a channel external to the combustion chamber, at least one wall of the channel being an outer wall of the combustion chamber.
8. 8. The process of claim 4 wherein, prior to mixing the air with the fuel, the compressed air is heated by heat radiating from the combustion chamber by passing said compressed air through a channel external to the combustion chamber, at least one wall of the channel being an outer wall of the combustion chamber.
9. 9. The process of claim 9 wherein the working fluid exiting the work engine contains less than 3 ppm NO_x.
10. 10. The process of claim 8 wherein the working fluid exiting the work engine contains less than 3 ppm CO.
11. 1 1 . The process of claim 8 wherein the working fluid exiting the work engine contains less than 3ppm CO and less than 3ppm NO_x.
12. 1 2. A power generating system comprising

    a) a combustion chamber, b) fuel supply means for delivering fuel to the combustion chamber, 48 c) air supply means for delivering compressed air at an elevated temperature and at a constant pressure to the combustion chamber the amount of air being chosen so that at least about 90% of the oxygen in the air is consumed when burned with the fuel, the fuel and air being mixed in the combustion chamber, d) control means to vary the quantity of air supplied to the combustion chamber and to adjust the amount of fuel supplied to the combustion chamber so that the fuel to air ratio remains constant, e) a fuel igniter for igniting the mixture of fuel and air to produce a combustion vapor stream, f) liquid supply means for delivering superheated water under pressure to the combustion chamber, the water being con- verted substantially instantaneously upon entering the combustion chamber to steam, the delivery and formation of steam creating turbulence and mixing in the combustion chamber resulting in a working fluid composed of steam, combustion products and non- flammable materials in the air and fuel, said working fluid being a high temperature steam stream deliverable to an external piece of equipment at a controlled pressure required by that external piece of equipment, g) a combustion chamber temperature controller, said controller delivering the superheated water to the combustion cham- ber in quantities sufficient to maintain the temperature of the working fluid at a desired level, substantially all of the control of the tempera- ture in the combustion chamber being derived from the latent heat of vaporization of the water introduced into the combustion chamber, and h) heat exchanging means for transferring heat from the working fluid exiting the work engine to the water, said heat elevat- 49 ing the temperature of the water from a feed temperature to the desired temperature for delivery to the combustion chamber.
13. 1 3. The power generating system of claim 1 2 wherein the water is non-potable water and the process further includes the collection of inor- ganic materials dissolved in the non-potable water in the combustion chamber and the conversion of the inorganic materials to a solid form and the combustion of organic materials dissolved therein or carried there with.
14. 1 4. The power generating system of claim 1 2 further including at least one heat transfer means positioned external and circumferential to the combustion chamber and extending along a substantial portion of the length of the combustion chamber such that the compressed air flows over external surfaces of the combustion chamber prior to entering the combus- tion chamber, the temperature of the compressed air being elevated by heat radiated from said external surfaces.
15. 1 5. The power generating system of claim 1 2 wherein the heat transfer means comprises at least two contiguous circumferential chambers.
16. 1 6. The power generating system of claim 1 2 also including the means for delivering additional water to the compressed air prior to intro- duction of the compressed air into the combustion chamber.